The invention provides a device and a method for monitoring and testing the real-time performance of optical Ethernet. A loop of the tested optical Ethernet is connected with two pieces of secondary equipment, and the device comprises optical splitters, optical fiber adapters, Ethernet message receiving and real-time analyzing modules, a human-computer interaction platform, a communication interface and IN ports and OU ports of optical fiber connectors, wherein every two optical splitters are connected into one tested optical fiber loop; the optical fiber adapters convert optical signals to digital signals containing message information and send the digital signals to the Ethernet message receiving and real-time analyzing modules; if central processing units judge the types of the received messages as the messages in a given monitoring type, the precise moments at which the messages are received are recorded and stored in a storer in the device; and the moments are either displayed through display modules or sent to a master station through the communication interface. A monitoring channel and an actual operational network channel are connected in parallel so as to be monitored and recorded, and the monitored message information is completely consistent with information moments received by real equipment.